U.S. patent number 10,785,871 [Application Number 16/218,395] was granted by the patent office on 2020-09-22 for panel molded electronic assemblies with integral terminals.
This patent grant is currently assigned to VLT, Inc.. The grantee listed for this patent is VLT, Inc.. Invention is credited to Michael B. LaFleur, Patrizio Vinciarelli.
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United States Patent |
10,785,871 |
Vinciarelli , et
al. |
September 22, 2020 |
Panel molded electronic assemblies with integral terminals
Abstract
Encapsulated electronic modules having complex contact
structures may be formed by encapsulating panels containing a
substrate comprising pluralities of electronic modules delineated
by cut lines and having conductive interconnects buried within
terminal holes and other holes drilled in the panel within the
boundaries of the cut lines. Slots may be cut in the panel along
the cut lines. The interior of the holes, as well as surfaces
within the slots and on the surfaces of the panel may be
metallized, e.g. by a series of processes including plating.
Terminals may be inserted into the terminal holes and connected to
conductive features or plating within the holes. A conductive
element may be provided on the substrate to connect to a terminal.
Alternatively solder may be dispensed into the holes for surface
mounting.
Inventors: |
Vinciarelli; Patrizio (Boston,
MA), LaFleur; Michael B. (East Hampstead, NH) |
Applicant: |
Name |
City |
State |
Country |
Type |
VLT, Inc. |
Andover |
MA |
US |
|
|
Assignee: |
VLT, Inc. (Andover,
MA)
|
Family
ID: |
1000004130106 |
Appl.
No.: |
16/218,395 |
Filed: |
December 12, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H05K
3/243 (20130101); H05K 1/184 (20130101); H05K
1/113 (20130101); H05K 1/181 (20130101); H05K
1/116 (20130101); H05K 3/3405 (20130101); H05K
3/429 (20130101) |
Current International
Class: |
H05K
1/11 (20060101); H05K 3/34 (20060101); H05K
1/18 (20060101); H05K 3/24 (20060101); H05K
3/42 (20060101); H01R 13/52 (20060101); H01L
21/56 (20060101); H05K 7/02 (20060101); H05K
1/14 (20060101); H05K 7/14 (20060101) |
Field of
Search: |
;174/261,254,255,262,265,266 ;361/736,752,826 ;257/678,758,773
;439/76.2,82,276,936 ;29/852 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
2863531 |
|
Apr 2015 |
|
EP |
|
H02280666 |
|
Nov 1990 |
|
JP |
|
H04293293 |
|
Oct 1992 |
|
JP |
|
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|
Primary Examiner: Chen; Xiaoliang
Attorney, Agent or Firm: Fish & Richardson P.C.
Claims
What is claimed is:
1. A method of forming electronic modules, the method comprising:
assembling an electronic module including a multilayer printed
circuit board ("PCB") having a plurality of conductive layers, a
first plurality of electronic components mounted to a first surface
of the PCB, and a first layer of cured encapsulant covering the
components and the surface of the PCB, the first layer of cured
encapsulant forming a first exterior surface of the module, the
electronic module including one or more conductive features buried
beneath the first exterior surface; selectively forming one or more
terminal holes in the first exterior surface through the first
layer by removing the cured encapsulant at predetermined locations
within perimeter boundaries of the electronic module, exposing
within the one or more terminal holes respective portions of the
one or more conductive features; inserting a conductive terminal
into each of the one or more terminal holes; and forming an
electrical connection between the conductive terminal and the
respective portions of the one or more conductive features exposed
within each of the one or more terminal holes; wherein the
selectively forming one or more terminal holes further comprises
using a laser; the one or more conductive features comprises a
conductive feature on the first surface of the PCB; wherein the
laser comprises a wavelength that removes encapsulant at a rate
that is at least an order of magnitude greater than a rate at which
material is removed from the conductive feature on the first
surface of the PCB; and wherein the one or more holes are limited
in depth by the conductive feature on the first surface of the
PCB.
2. The method of claim 1, further comprising selectively forming
one or more conductive metal layers on the first exterior surface
and on a sidewall surface within each of selected terminal holes in
electrical contact with the respective portions of the one or more
conductive features exposed within the selected terminal holes.
3. The method of claim 2 wherein the one or more conductive
features further comprise at least one of the conductive layers, at
least one of the terminal holes are formed through a portion of the
PCB, and the respective portions of the one or more conductive
features include edges of the at least one of the conductive
layers.
4. The method of claim 2 wherein the forming an electrical
connection includes for each selected terminal hole soldering the
respective conductive terminal to the conductive metal layer within
the selected terminal hole or the respective portions of the one or
more conductive features exposed within the selected terminal hole,
or both.
5. The method of claim 4 wherein each respective conductive
terminal comprises a columnar portion extending beyond the first
exterior surface of the electronic module and being adapted to
engage with a through hole in a second printed circuit board
external to the electronic module.
6. The method of claim 4 wherein each respective conductive
terminal comprises a threaded hole adapted to accept a threaded
fastener.
7. The method of claim 1 wherein the forming an electrical
connection for selected terminal holes includes forming a pressure
fit between the respective conductive terminal and the respective
portions of the one or more conductive features exposed within the
selected terminal holes.
8. The method of claim 4 wherein the selected terminal holes each
have a circular cross-section and each respective terminal includes
a portion lying within each selected terminal hole having
indentations providing gaps between the portion of the terminal and
the sidewall surface of the hole.
9. The method of claim 8 wherein the indentations are adapted to
allow gases to escape from the selected holes during the
soldering.
10. The method of claim 8 wherein the indentations include features
adapted to resist rotation of the terminal in the terminal
hole.
11. The method of claim 1 wherein the assembling the electronic
module includes mounting at least one conductive component to the
PCB, the at least one conductive component being covered by the
first layer of cured encapsulant, and wherein forming the one or
more terminal holes includes exposing the conductive component in a
respective one of the terminal holes.
12. The method of claim 11 wherein the conductive component
includes a hole feature covered by the first layer of cured
encapsulant and approximately aligned with a location of the
respective one of the terminal holes, and the forming the
respective one of the terminal holes exposes the hole feature.
13. The method of claim 2 wherein the forming one or more
conductive metal layers includes patterning to produce a metal pad
on an external surface of the electronic module surrounding the
terminal holes, the metal forming the pad being continuous with the
metal extending into the at least one terminal hole and the metal
pad providing an electrical contact on the external surface
connected to the one or more exposed features; and wherein the
forming an electrical connection includes soldering the conductive
terminal to the metal within the selected terminal hole or the pad
on the external surface, or both.
14. The method of claim 1, further comprising selectively forming
one or more conductive metal layers on a sidewall surface within
each of selected terminal holes in electrical contact with the
respective portions of the one or more conductive features exposed
within the selected terminal holes.
15. The method of claim 1, further comprising: selectively forming
one or more mounting holes in the first exterior surface through
the first layer at predetermined locations within perimeter
boundaries of the electronic module, each mounting hole
intersecting a respective second set of the conductive features to
expose respective portions of the respective second set of
conductive features in the respective mounting hole; selectively
forming one or more conductive metal layers on the first external
surface and on a sidewall surface within each of selected mounting
holes in electrical contact with the exposed respective portions of
the respective second set of conductive features in the respective
mounting hole to form a conductive metal mounting pad on the first
exterior surface surrounding the respective mounting hole, the
metal mounting pad being continuous with the one or more conductive
metal layers on the interior surface of the respective mounting
hole and providing an electrical contact on the first exterior
surface connected to the exposed respective portions of the
respective second set of the conductive features.
16. The method of claim 15, further comprising patterning the one
or more metal layers on the first exterior surface to form a metal
shield electrically connected to at least one of the metal mounting
pads and covering at least 25 percent of the first exterior
surface.
17. The method of claim 16 wherein the metal shield covers at least
50 percent of the exterior module surface and connects a plurality
of the mounting holes.
18. The method of claim 15 wherein at least one of the mounting
holes extends completely through the module.
19. The method of claim 2 wherein assembling the electronic module
comprises providing a PCB panel, mounting a plurality of electronic
components to first and second surfaces of the PCB panel,
encapsulating the PCB panel and electronic components to form an
encapsulated panel, the encapsulated panel comprising a plurality
of the electronic modules, and cutting the encapsulated panel to
singulate the electronic modules.
20. The method of claim 19 wherein the cutting step is performed
after the steps of forming the terminal holes and forming one or
more conductive metal layers.
21. The method of claim 20 wherein the cutting is performed after
the step of inserting the conductive terminal.
22. The method of claim 20 wherein the cutting is performed before
the step of inserting the conductive terminal.
23. The method of claim 2 in which selectively forming one or more
conductive metal layers on a sidewall surface within each of
selected terminal holes comprises forming a conductive path from
the one or more conductive metal layers on the first exterior
surface through the layer of cured encapsulant to the one or more
conductive features exposed within the selected terminal holes.
24. The method of claim 2 in which selectively forming one or more
conductive metal layers on a sidewall surface within each of
selected terminal holes comprises selectively forming one or more
conductive metal layers on a portion of the sidewall surface made
of the cured encapsulant within each of selected terminal
holes.
25. A method of forming electronic modules, the method comprising:
assembling an electronic module including a multilayer printed
circuit board ("PCB") having a plurality of conductive layers, a
first plurality of electronic components mounted to a first surface
of the PCB, and a first layer of cured encapsulant covering the
components and the surface of the PCB, the first layer of cured
encapsulant forming a first exterior surface of the module, the
electronic module including one or more conductive features buried
beneath the first exterior surface; selectively forming one or more
terminal holes in the first exterior surface through the first
layer by removing the cured encapsulant at predetermined locations
within perimeter boundaries of the electronic module, exposing
within the one or more terminal holes respective portions of the
one or more conductive features; inserting a conductive terminal
into each of the one or more terminal holes; forming an electrical
connection between the conductive terminal and the respective
portions of the one or more conductive features exposed within each
of the one or more terminal holes; selectively forming one or more
mounting holes in the first exterior surface through the first
layer at predetermined locations within perimeter boundaries of the
electronic module, each mounting hole intersecting a respective
second set of the conductive features to expose respective portions
of the respective second set of conductive features in the
respective mounting hole; and selectively forming one or more
conductive metal layers on the first external surface and on a
sidewall surface within each of selected mounting holes in
electrical contact with the exposed respective portions of the
respective second set of conductive features in the respective
mounting hole to form a conductive metal mounting pad on the first
exterior surface surrounding the respective mounting hole, the
metal mounting pad being continuous with the one or more conductive
metal layers on the interior surface of the respective mounting
hole and providing an electrical contact on the first exterior
surface connected to the exposed respective portions of the
respective second set of the conductive features.
26. The method of claim 25, further comprising selectively forming
one or more conductive metal layers on the first exterior surface
and on a sidewall surface within each of selected terminal holes in
electrical contact with the respective portions of the one or more
conductive features exposed within the selected terminal holes.
27. The method of claim 25 wherein the one or more conductive
features further comprise at least one of the conductive layers, at
least one of the terminal holes are formed through a portion of the
PCB, and the respective portions of the one or more conductive
features include edges of the at least one of the conductive
layers.
28. The method of claim 25 wherein the forming an electrical
connection includes for each selected terminal hole soldering the
respective conductive terminal to the conductive metal layer within
the selected terminal hole or the respective portions of the one or
more conductive features exposed within the selected terminal hole,
or both.
29. The method of claim 25 wherein each respective conductive
terminal comprises a columnar portion extending beyond the first
exterior surface of the electronic module and being adapted to
engage with a through hole in a second printed circuit board
external to the electronic module.
30. The method of claim 25 wherein each respective conductive
terminal comprises a threaded hole adapted to accept a threaded
fastener.
31. The method of claim 25 wherein the forming an electrical
connection for selected terminal holes includes forming a pressure
fit between the respective conductive terminal and the respective
portions of the one or more conductive features exposed within the
selected terminal holes.
32. The method of claim 25 wherein the selected terminal holes each
have a circular cross-section and each respective terminal includes
a portion lying within each selected terminal hole having
indentations providing gaps between the portion of the terminal and
the sidewall surface of the hole.
33. The method of claim 32 wherein the indentations are adapted to
allow gases to escape from the selected holes during the
soldering.
34. The method of claim 32 wherein the indentations include
features adapted to resist rotation of the terminal in the terminal
hole.
35. The method of claim 25 wherein the conductive component
includes a hole feature covered by the first layer of cured
encapsulant and approximately aligned with a location of the
respective one of the terminal holes, and the forming the
respective one of the terminal holes exposes the hole feature.
36. The method of claim 26 wherein the forming one or more
conductive metal layers includes patterning to produce a metal pad
on an external surface of the electronic module surrounding the
terminal holes, the metal forming the pad being continuous with the
metal extending into the at least one terminal hole and the metal
pad providing an electrical contact on the external surface
connected to the one or more exposed features; and wherein the
forming an electrical connection includes soldering the conductive
terminal to the metal within the selected terminal hole or the pad
on the external surface, or both.
37. The method of claim 25, further comprising selectively forming
one or more conductive metal layers on a sidewall surface within
each of selected terminal holes in electrical contact with the
respective portions of the one or more conductive features exposed
within the selected terminal holes.
38. The method of claim 25, further comprising patterning the one
or more metal layers on the first exterior surface to form a metal
shield electrically connected to at least one of the metal mounting
pads and covering at least 25 percent of the first exterior
surface.
39. The method of claim 38 wherein the metal shield covers at least
50 percent of the exterior module surface and connects a plurality
of the mounting holes.
40. The method of claim 25 wherein at least one of the mounting
holes extends completely through the module.
41. The method of claim 25 wherein assembling the electronic module
comprises providing a PCB panel, mounting a plurality of electronic
components to first and second surfaces of the PCB panel,
encapsulating the PCB panel and electronic components to form an
encapsulated panel, the encapsulated panel comprising a plurality
of the electronic modules, and cutting the encapsulated panel to
singulate the electronic modules.
42. The method of claim 41 wherein the cutting step is performed
after the steps of forming the terminal holes and forming one or
more conductive metal layers.
43. The method of claim 41 wherein the cutting is performed after
the step of inserting the conductive terminal.
44. The method of claim 41 wherein the cutting is performed before
the step of inserting the conductive terminal.
45. The method of claim 26 in which selectively forming one or more
conductive metal layers on a sidewall surface within each of
selected terminal holes comprises forming a conductive path from
the one or more conductive metal layers on the first exterior
surface through the layer of cured encapsulant to the one or more
conductive features exposed within the selected terminal holes.
46. The method of claim 26 in which selectively forming one or more
conductive metal layers on a sidewall surface within each of
selected terminal holes comprises selectively forming one or more
conductive metal layers on a portion of the sidewall surface made
of the cured encapsulant within each of selected terminal
holes.
47. A method of forming electronic modules, the method comprising:
assembling an electronic module including a multilayer printed
circuit board ("PCB") having a plurality of conductive layers, a
first plurality of electronic components mounted to a first surface
of the PCB, and a first layer of cured encapsulant covering the
components and the surface of the PCB, the first layer of cured
encapsulant forming a first exterior surface of the module, the
electronic module including one or more conductive features buried
beneath the first exterior surface; selectively forming one or more
terminal holes in the first exterior surface through the first
layer by removing the cured encapsulant at predetermined locations
within perimeter boundaries of the electronic module, exposing
within the one or more terminal holes respective portions of the
one or more conductive features; inserting a conductive terminal
into each of the one or more terminal holes; forming an electrical
connection between the conductive terminal and the respective
portions of the one or more conductive features exposed within each
of the one or more terminal holes; and selectively forming one or
more conductive metal layers on the first exterior surface and on a
sidewall surface within each of selected terminal holes in
electrical contact with the respective portions of the one or more
conductive features exposed within the selected terminal holes;
wherein assembling the electronic module comprises providing a PCB
panel, mounting a plurality of electronic components to first and
second surfaces of the PCB panel, encapsulating the PCB panel and
electronic components to form an encapsulated panel, the
encapsulated panel comprising a plurality of the electronic
modules, and cutting the encapsulated panel to singulate the
electronic modules.
48. The method of claim 47 wherein the one or more conductive
features further comprise at least one of the conductive layers, at
least one of the terminal holes are formed through a portion of the
PCB, and the respective portions of the one or more conductive
features include edges of the at least one of the conductive
layers.
49. The method of claim 47 wherein the forming an electrical
connection includes for each selected terminal hole soldering the
respective conductive terminal to the conductive metal layer within
the selected terminal hole or the respective portions of the one or
more conductive features exposed within the selected terminal hole,
or both.
50. The method of claim 47 wherein each respective conductive
terminal comprises a columnar portion extending beyond the first
exterior surface of the electronic module and being adapted to
engage with a through hole in a second printed circuit board
external to the electronic module.
51. The method of claim 47 wherein each respective conductive
terminal comprises a threaded hole adapted to accept a threaded
fastener.
52. The method of claim 47 wherein the forming an electrical
connection for selected terminal holes includes forming a pressure
fit between the respective conductive terminal and the respective
portions of the one or more conductive features exposed within the
selected terminal holes.
53. The method of claim 47 wherein the selected terminal holes each
have a circular cross-section and each respective terminal includes
a portion lying within each selected terminal hole having
indentations providing gaps between the portion of the terminal and
the sidewall surface of the hole.
54. The method of claim 53 wherein the indentations are adapted to
allow gases to escape from the selected holes during the
soldering.
55. The method of claim 53 wherein the indentations include
features adapted to resist rotation of the terminal in the terminal
hole.
56. The method of claim 47 wherein the forming one or more
conductive metal layers includes patterning to produce a metal pad
on an external surface of the electronic module surrounding the
terminal holes, the metal forming the pad being continuous with the
metal extending into the at least one terminal hole and the metal
pad providing an electrical contact on the external surface
connected to the one or more exposed features; and wherein the
forming an electrical connection includes soldering the conductive
terminal to the metal within the selected terminal hole or the pad
on the external surface, or both.
57. The method of claim 47, further comprising selectively forming
one or more conductive metal layers on a sidewall surface within
each of selected terminal holes in electrical contact with the
respective portions of the one or more conductive features exposed
within the selected terminal holes.
58. The method of claim 47 wherein the cutting step is performed
after the steps of forming the terminal holes and forming one or
more conductive metal layers.
59. The method of claim 47 wherein the cutting is performed after
the step of inserting the conductive terminal.
60. The method of claim 47 wherein the cutting is performed before
the step of inserting the conductive terminal.
61. The method of claim 47 wherein the selectively forming one or
more terminal holes further comprises using a laser; the one or
more conductive features comprises a conductive feature on the
first surface of the PCB; wherein the laser comprises a wavelength
that removes encapsulant at a rate that is at least an order of
magnitude greater than a rate at which material is removed from the
conductive feature on the first surface of the PCB; and wherein the
one or more holes are limited in depth by the conductive feature on
the first surface of the PCB.
62. The method of claim 47 in which selectively forming one or more
conductive metal layers on a sidewall surface within each of
selected terminal holes comprises forming a conductive path from
the one or more conductive metal layers on the first exterior
surface through the layer of cured encapsulant to the one or more
conductive features exposed within the selected terminal holes.
63. The method of claim 47 in which selectively forming one or more
conductive metal layers on a sidewall surface within each of
selected terminal holes comprises selectively forming one or more
conductive metal layers on a portion of the sidewall surface made
of the cured encapsulant within each of selected terminal
holes.
64. A method of forming electronic modules, the method comprising:
assembling an electronic module including a multilayer printed
circuit board ("PCB") having a plurality of conductive layers, a
first plurality of electronic components mounted to a first surface
of the PCB, and a first layer of cured encapsulant covering the
components and the surface of the PCB, the first layer of cured
encapsulant forming a first exterior surface of the module, the
electronic module including one or more conductive features buried
beneath the first exterior surface; selectively forming one or more
terminal holes in the first exterior surface through the first
layer by removing the cured encapsulant at predetermined locations
within perimeter boundaries of the electronic module, exposing
within the one or more terminal holes respective portions of the
one or more conductive features, inserting a conductive terminal
into each of the one or more terminal holes; and forming an
electrical connection between the conductive terminal and the
respective portions of the one or more conductive features exposed
within each of the one or more terminal holes; wherein the
assembling the electronic module includes mounting at least one
conductive component to the PCB, the at least one conductive
component being covered by the first layer of cured encapsulant,
and wherein forming the one or more terminal holes includes
exposing the conductive component in a respective one of the
terminal holes.
65. The method of claim 64, further comprising selectively forming
one or more conductive metal layers on the first exterior surface
and on a sidewall surface within each of selected terminal holes in
electrical contact with the respective portions of the one or more
conductive features exposed within the selected terminal holes.
66. The method of claim 64 wherein the one or more conductive
features further comprise at least one of the conductive layers, at
least one of the terminal holes are formed through a portion of the
PCB, and the respective portions of the one or more conductive
features include edges of the at least one of the conductive
layers.
Description
FIELD OF THE INVENTION
This invention relates to the field of encapsulated electronic
assemblies, including encapsulated power converters, and more
particularly to providing externally accessible connection
terminals that provide a conductive path to elements within the
encapsulated assembly.
BACKGROUND
An encapsulated electronic module, such as an electronic power
converter module for example, may comprise a printed circuit
assembly over-molded with an encapsulant to form some or all of the
package and exterior structure or surfaces of the module.
Encapsulation in this manner may aid in conducting heat out of the
over-molded components, i.e., components that are mounted on the
printed circuit assembly and covered with encapsulant. It is
necessary to provide means for making electrical connections
between the internal printed circuit assembly and external
circuitry (e.g. an external printed circuit board; a socket). There
are many known ways to make such connections, including, but not
limited to, lead frames, pins, conductive terminals and flexible
wire leads.
SUMMARY
In general, in one aspect, a method of forming electronic modules
is provided. The method includes: assembling an electronic module
including a multilayer printed circuit board ("PCB") having a
plurality of conductive layers, a first plurality of electronic
components mounted to a first surface of the PCB, and a first layer
of cured encapsulant covering the components and the surface of the
PCB, the first layer of cured encapsulant forming a first exterior
surface of the module, the electronic module including one or more
conductive features buried beneath the first exterior surface;
selectively forming one or more terminal holes in the first
exterior surface through the first layer at predetermined locations
within perimeter boundaries of the electronic module, exposing
within the one or more terminal holes respective portions of the
one or more conductive features; inserting a conductive terminal
into each of the one or more terminal holes; and forming an
electrical connection between the conductive terminal and the
respective portions of the one or more conductive features exposed
within each of the one or more terminal holes.
Implementations of the aspect can include one or more of the
following features. The method can further include selectively
forming one or more conductive metal layers on the first exterior
surface and on a sidewall surface within each of selected terminal
holes in electrical contact with the respective portions of the one
or more conductive features exposed within the selected terminal
holes. The one or more conductive features further can include at
least one of the conductive layers, at least one of the terminal
holes are formed through a portion of the PCB, and the respective
portions of the one or more conductive features include edges of
the at least one of the conductive layers. Forming an electrical
connection can include, for each selected terminal hole, soldering
the respective conductive terminal to the conductive metal layer
within the selected terminal hole or the respective portions of the
one or more conductive features exposed within the selected
terminal hole, or both. Each respective conductive terminal can
include a columnar portion that extends beyond the first exterior
surface of the electronic module and can be adapted to engage with
a through hole in a second printed circuit board external to the
electronic module. Each respective conductive terminal can include
a threaded hole adapted to accept a threaded fastener.
Forming an electrical connection for selected terminal holes can
include forming a pressure fit between the respective conductive
terminal and the respective portions of the one or more conductive
features exposed within the selected terminal holes. The selected
terminal holes each can have a circular cross-section and each
respective terminal can include a portion lying within each
selected terminal hole having indentations providing gaps between
the portion of the terminal and the sidewall surface of the hole.
The indentations can be adapted to allow gases to escape from the
selected holes during the soldering. The indentations can include
features adapted to resist rotation of the terminal in the terminal
hole. Assembling the electronic module can include mounting at
least one conductive component to the PCB, the at least one
conductive component can be covered by the first layer of cured
encapsulant, and forming the one or more terminal holes can include
exposing the conductive component in a respective one of the
terminal holes. The conductive component can include a hole feature
covered by the first layer of cured encapsulant and approximately
aligned with a location of the respective one of the terminal
holes, and the respective one of the terminal holes can expose the
hole feature.
Forming one or more conductive metal layers can include patterning
to produce a metal pad on an external surface of the electronic
module surrounding the terminal holes, the metal forming the pad
can be continuous with the metal extending into the at least one
terminal hole, and the metal pad can provide an electrical contact
on the external surface connected to the one or more exposed
features. Forming an electrical connection can include soldering
the conductive terminal to the metal within the selected terminal
hole or the pad on the external surface, or both. The method can
further include selectively forming one or more conductive metal
layers on a sidewall surface within each of selected terminal holes
in electrical contact with the respective portions of the one or
more conductive features exposed within the selected terminal
holes.
The method can further include: selectively forming one or more
mounting holes in the first exterior surface through the first
layer at predetermined locations within perimeter boundaries of the
electronic module, each mounting hole intersecting a respective
second set of the conductive features to expose respective portions
of the respective second set of conductive features in the
respective mounting hole. The method can further include:
selectively forming one or more conductive metal layers on the
first external surface and on a sidewall surface within each of
selected mounting holes in electrical contact with the exposed
respective portions of the respective second set of conductive
features in the respective mounting hole to form a conductive metal
mounting pad on the first exterior surface surrounding the
respective mounting hole, the metal mounting pad being continuous
with the one or more conductive metal layers on the interior
surface of the respective mounting hole and providing an electrical
contact on the first exterior surface connected to the exposed
respective portions of the respective second set of the conductive
features.
The method can further include patterning the one or more metal
layers on the first exterior surface to form a metal shield
electrically connected to at least one of the metal mounting pads
and covering at least 25 percent of the first exterior surface. The
metal shield can cover at least 50% of the exterior module surface
and connect a plurality of the mounting holes. At least one of the
mounting holes can extend completely through the module. Assembling
the electronic module can include providing a PCB panel, mounting a
plurality of electronic components to first and second surfaces of
the PCB panel, encapsulating the PCB panel and electronic
components to form an encapsulated panel, the encapsulated panel
comprising a plurality of the electronic modules, and cutting the
encapsulated panel to singulate the electronic modules. In some
examples, the cutting step can be performed after the steps of
forming the terminal holes and forming one or more conductive metal
layers. In some examples, the cutting can be performed after the
step of inserting the conductive terminal. In some examples, the
cutting can be performed before the step of inserting the
conductive terminal. Selectively forming one or more terminal holes
can further include using a laser, and the one or more conductive
features can include a conductive feature on the first surface of
the PCB. The laser can include a wavelength that removes
encapsulant at a rate that is at least an order of magnitude
greater than a rate at which material is removed from the
conductive feature on the first surface of the PCB. The one or more
holes can be limited in depth by the conductive feature on the
first surface of the PCB.
In general, in another aspect, apparatus includes an electronic
module including a multilayer printed circuit board ("PCB") having
a plurality of conductive layers, a first plurality of electronic
components mounted to a first surface of the PCB, and a first layer
of cured encapsulant covering the first plurality of components and
the first surface of the PCB, the first layer of cured encapsulant
forming a first exterior module surface. The apparatus includes one
or more conductive features buried beneath the first exterior
module surface; and one or more terminal holes formed in the first
layer of cured encapsulant, each terminal hole intersecting a
respective set of the conductive features to expose respective
portions of the selected set of the conductive features and having
a respective conductive terminal within the terminal hole and
electrically connected to the respective portions of the respective
set of conductive features.
Implementations of the aspect can include one or more of the
following features. The apparatus can include a conductive metal
layer formed on an interior surface of selected terminal holes in
contact with the respective portions of the respective set of
conductive features within the respective terminal hole. The
selected set of conductive features can include one or more of the
conductive layers of the PCB, each selected terminal hole can be
formed through at least a portion of the PCB, and the respective
portions of the one or more conductive features can include edges
of the one or more conductive layers. The apparatus can further
include a conductive metal pad formed on the first exterior module
surface surrounding one or more of the selected terminal holes, the
metal pad can be continuous with the conductive metal layer on the
interior surface of the one or more of the selected terminal holes
and provide an electrical contact on the first exterior module
surface connected to the one or more exposed features within the
respective terminal hole. The apparatus can further include a
solder connection between a portion of the conductive terminal and
the conductive metal layer on the interior surface of the one or
more selected terminal holes. The apparatus can further include a
solder connection between a portion of the conductive terminal the
conductive metal pad.
The apparatus can further include one or more mounting holes formed
in the first layer of cured encapsulant, each mounting hole can
intersect a respective second set of the conductive features to
expose respective portions of the respective second set of
conductive features in the respective mounting hole. Each mounting
hole can have a conductive metal layer formed on an interior
surface of the respective mounting hole in contact with the exposed
respective portions of the respective second set of conductive
features within the respective mounting hole and a conductive metal
mounting pad formed on the exterior module surface surrounding the
respective mounting hole, and the metal mounting pad can be
continuous with the conductive metal layer on the interior surface
of the respective mounting hole and providing an electrical contact
on the exterior module surface connected to the exposed respective
portions of the respective second set of the conductive features.
The metal mounting pad can further include a conductive metal
shield covering a at least 25 percent of the exterior module
surface. The conductive shield can cover at least 50 percent of the
exterior module surface and connect a plurality of the mounting
holes. The mounting holes can extend completely through the
electronic module. The electronic module can further include a
second set of electronic components mounted to a second surface of
the PCB, a second layer of cured encapsulant can cover the second
set of components and the second surface of the PCB, and the second
layer of cured encapsulant can form a second exterior module
surface.
The apparatus can further include a conductive metal layer formed
on an interior surface of each of selected terminal holes in
contact with the respective portions of the respective set of
conductive features within the respective terminal hole. The
selected set of conductive features can include one or more of the
conductive layers of the PCB, each selected terminal hole can be
formed through at least a portion of the PCB, and the respective
portions of the one or more conductive features can include edges
of the one or more conductive layers. The apparatus can further
include a conductive metal pad formed on the first exterior module
surface surrounding one or more of the selected terminal holes, and
the metal pad can be continuous with the conductive metal layer on
the interior surface of the one or more of the selected terminal
holes and provide an electrical contact on the first exterior
module surface connected to the one or more exposed features within
the respective terminal hole. The apparatus can further include a
solder connection between a portion of the conductive terminal and
the conductive metal layer on the interior surface of the one or
more selected terminal holes. The apparatus can further include a
solder connection between a portion of the conductive terminal and
the conductive metal pad.
The apparatus can further include one or more mounting holes formed
in the first and second layers of cured encapsulant and PCB, each
mounting hole can extend completely through the module and
intersect a respective second set of the conductive features to
expose respective portions of the respective second set of
conductive features in the respective mounting hole. Each mounting
hole can have a conductive metal layer formed on an interior
surface of the respective mounting hole in contact with the exposed
respective portions of the respective second set of conductive
features within the respective mounting hole and a conductive metal
mounting pad formed on one or both of the first and second exterior
module surfaces surrounding the respective mounting hole, and the
metal mounting pad can be continuous with the conductive metal
layer on the interior surface of the respective mounting hole and
provide an electrical contact on the exterior module surface
connected to the exposed respective portions of the respective
second set of the conductive features. The metal mounting pad can
further include a conductive metal shield covering a at least 25
percent of one or both of the first and second exterior module
surfaces. The conductive shield can cover at least 50 percent of
both of the first and second exterior module surfaces and
electrically connect to a plurality of the mounting holes. The
selected set of conductive features can include a conductive trace
on a surface of the PCB, each selected terminal hole can be limited
in depth to the surface of the PCB, and the respective portions of
the one or more conductive features can include a surface of the
conductive trace at a bottom of each terminal hole.
In another general aspect, a method of forming modular circuit
assemblies is provided. The method includes: assembling an
encapsulated panel including a multilayer printed circuit board
("PCB") having a plurality of conductive layers, a first plurality
of electronic components mounted to a first surface of the PCB, and
a first layer of cured encapsulant covering the first plurality of
electronic components and the surface of the PCB, the first layer
of cured encapsulant forming a first exterior surface of the
encapsulated panel, the encapsulated panel comprising a plurality
of unsingulated electronic modules, each module having perimeter
boundaries defined by one or more predetermined cut lines and one
or more conductive features buried beneath the first exterior
surface; selectively forming a plurality of terminal holes in the
first exterior surface of the panel through the first layer at
predetermined locations within the perimeter boundaries of each
electronic module, each terminal hole being spaced apart from the
cut lines and exposing within the hole a respective conductive
feature; selectively forming one or more conductive metal layers on
the first exterior surface of the panel including within the
plurality of terminal holes, the one or more conductive metal
layers within each terminal hole being in electrical contact with
the respective conductive feature; patterning the one or more
conductive metal layers on the exterior surface, to form a
plurality of electrical contacts on the exterior surface of the
panel electrically isolated from at least one other electrical
contact in the plurality of electrical contacts; and cutting the
panel along the one or more cut lines to singulate the plurality of
electronic modules, each singulated electronic module having a
respective plurality of the electrical contacts formed on the
exterior surface of the module.
Implementations of the aspect can include one or more of the
following features. The method can further include selectively
dispensing solder to each of the terminal holes, at least partially
filling each terminal hole with solder. The method can further
include applying a compressive force to the dispensed solder to
establish a predetermined uniform height relative to the first
exterior surface. The method can further include selectively
dispensing a curable compound to each of the of terminal holes, at
least partially filling each terminal hole with the curable
compound, curing the compound; and selectively dispensing solder to
each of the terminal holes, at least partially further filling each
terminal hole with solder. The method can further include applying
a compressive force to the dispensed solder to establish a
predetermined uniform height relative to the first exterior
surface. Selectively forming a plurality of terminal holes can
further include using a laser; the respective conductive feature
can include a conductive trace on the first surface of the PCB; the
laser can include a wavelength that removes encapsulant at a rate
that is at least an order of magnitude greater than a rate at which
material would be removed from the conductive trace; and the
plurality of terminal holes can be formed at a depth that is
limited by the respective conductive trace on the surface of the
PCB.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 shows an isometric view of an electronic module.
FIG. 2 is an exploded view showing terminals prior to insertion in
plated holes.
FIG. 3 shows an isometric view of an encapsulated panel comprising
several electronic modules included in regions defined by cut
lines.
FIG. 4 shows the panel of FIG. 3 comprising slots cut along the cut
lines.
FIG. 5 shows the panel of FIG. 4 after metallization.
FIG. 6 shows a portion of the panel of FIG. 5 after
singulation.
FIG. 7A shows a cross section of a terminal hole in an electronic
module that passes entirely through an internal substrate.
FIG. 7B shows a cross section of a terminal hole in an electronic
module that does not penetrate an internal substrate.
FIG. 7C shows a cross section of terminal holes in an electronic
module that pass partially and completely through an internal
substrate.
FIGS. 8A and 8B are cross-sectional views of a terminal soldered
into a plated hole.
FIGS. 9A and 9B are cross-sectional views showing both soldered and
press-fit terminals in plated holes.
FIG. 10 shows a conductive feature on a surface of the internal
substrate.
FIGS. 11A, 11B, 11C and 11D are cross-sectional views showing
configurations of conductive components on the surfaces of an
internal substrate.
FIG. 12 shows a press-fit pin.
FIG. 13 shows a magnified portion of FIG. 9A.
FIG. 14 shows an isometric view of an electronic module.
FIGS. 15 and 16 show isometric views of the module of FIG. 14
mounted to an external printed circuit board.
FIG. 17 shows an exploded isometric view of a configuration in
which external connections to an electronic module comprise ring
lugs.
FIG. 18A shows a modified panel with cut lines after
metallization.
FIG. 18B shows the panel of FIG. 18A after solder deposition.
FIGS. 19A and 19B show process flow charts for fabricating the
modules.
Like reference numbers and symbols in the various drawings indicate
like elements.
DETAILED DESCRIPTION
An encapsulated electronic module, such as an electronic power
converter module for example, may comprise a printed circuit
assembly over-molded with an encapsulant to form some or all of the
package and exterior structure or surfaces of the module. In the
case of an electronic power converter module, the printed circuit
assembly may include one or more inductive components, such as
inductors and transformers. Encapsulated electronic power
converters capable of being surface mount soldered to a customer
motherboard are described in Vinciarelli et al., Power Converter
Package and Thermal Management, U.S. Pat. No. 7,361,844, issued
Apr. 22, 2008, (the "SAC Package Patent") (assigned to VLT, Inc. of
Andover, Mass., the entire disclosure of which is incorporated
herein by reference). Encapsulated electronic modules having at
least one surface of a magnetic core structure exposed and methods
for manufacturing the same are described in Vinciarelli et al.,
Encapsulation Method and Apparatus for Electronic Modules, U.S.
Pat. No. 8,427,269 issued Apr. 23, 2013, (the "Exposed Core
Patent") (assigned to VI Chip Inc. of Andover, Mass., the entire
disclosure of which is incorporated herein by reference). Methods
of making encapsulated multi-cell power converters and
interconnection modules are described in Vinciarelli, Delivering
Power to Semiconductor Loads, U.S. patent application Ser. No.
16/218,418, filed Dec. 12, 2018, (the "Gearbox Disclosure")
(assigned to VLT, Inc. of Andover, Mass., the entire disclosure of
which is incorporated herein by reference).
Methods of over-molding both sides of a printed circuit board
assembly while leaving opposing regions on both sides of the
printed circuit board free of encapsulant are described in Saxelby,
et al., Circuit Encapsulation Process, U.S. Pat. No. 5,728,600,
issued Mar. 17, 1998 and Saxelby, et al., Circuit Encapsulation,
U.S. Pat. No. 6,403,009, issued Jun. 11, 2002 (collectively the
"Molding Patents") (both assigned to VLT, Inc. of Andover, Mass.
and incorporated by reference in their entirety).
Encapsulation of multiple electronic assemblies as panels followed
by singulation into individual modules and forming electrical
contacts, e.g. "bar codes," along vertical edges of individual
modules, e.g. during singulation from the panel, for establishing
electrical connections to the circuitry inside each module are
described in Vinciarelli et al., Panel-Molded Electronic
Assemblies, U.S. Pat. No. 8,966,747, issued on Mar. 3, 2015 (the
"Bar Code Patent"); and in Vinciarelli et al., Panel-Molded
Electronic Assemblies, U.S. Pat. No. 9,402,319, issued on Jul. 26,
2016 (the "PM CIP"); enhanced three-dimensional contacts for
establishing robust solder connections to the bar codes is
described in Vinciarelli et al., Electronic Assemblies Having
Components With Edge Connectors, U.S. patent application Ser. No.
14/596,914, filed on Jan. 14, 2015 (the "3D Bar Code Application");
encapsulation of multiple electronic assemblies as a panel, and
forming electrical contacts on multiple faces of each electronic
assembly, including vertical and horizontal faces, prior to
singulation of the panel into modules, is described in Vinciarelli
et al., Panel Molded Electronic Assemblies With Multi-Surface
Conductive Contacts, U.S. patent application Ser. No. 14/731,287,
filed on Jun. 4, 2015 (the "Multi-Surface Application");
collectively the "Panel Mold Disclosures" (all of which are
assigned to VLT, Inc. of Andover, Mass., and are incorporated in
their entirety herein by reference). The Panel Mold Disclosures
describe processes for making pluralities of electronic modules in
encapsulated panels, which may have interconnection features buried
within the encapsulated panel, e.g. in a PCB encapsulated within
the panel, and which are subsequently singulated into individual
electronic modules.
I. Terminal Inserts
Referring to FIG. 1, an electronic module 100 is shown having a
plurality of electrical terminals, e.g. 130-1, 130-2, 140-1, 140-2,
and 170. The electric terminals can be made of, e.g., electrically
conductive metal. The electronic module includes a printed circuit
board 101 ("PCB") (which can be, e.g., a multilayer printed circuit
board) disposed between cured layers of encapsulant 102 and 103.
The PCB 101 may have electronic components, and conductive runs or
traces and other conductive features, mounted to its surfaces and
enclosed within the encapsulant layers. The PCB 101 may have one or
more conductive layers disposed within the PCB 101, such that
portions of the conductive layers are not exposed until holes are
formed in the PCB 101 to expose the portions of the conductive
layers. The terminals, which may extend into, but preferably not
all the way through, the module 100 provide means for making
external connections to circuitry on the encapsulated PCB 101. As
shown in FIG. 1, relatively large electrical contacts, e.g.
contacts 130-1, 130-2, 140-1, 140-2 (each of which may include a
threaded hole to receive a threaded fastener, such as a screw, see,
e.g. screws 970-1, 970-2, 970-3, 970-4 in FIG. 17) provide
relatively higher current carrying capacity, making them amenable
for use as power connections. In the power converter example shown,
contacts 140-1 and 140-2 may, e.g., be used for input power
connections, and contacts 130-1 and 130-2 may, e.g., be used for
output power connections. A plurality of smaller terminals 170,
having relatively smaller interconnect area and lower current
carrying capacity, may be provided for low current inputs or
outputs or for signal connections, such as control and
communication signals.
Additionally, as shown in FIG. 1, portions of the outer surfaces of
the encapsulant layers 102, 103 and the edges of PCB 101
(optionally including areas covering magnetic cores (not shown), as
described e.g., in the Exposed Core patent), may be coated with an
electrically (and thermally) conductive shield 150. The shield 150,
which may, e.g. be made of copper, may serve one or more functions,
e.g. provide a grounding surface and/or an electromagnetic shield
(e.g. for EMI reduction), improve heat distribution over the large
surfaces of the module (e.g. provide isothermal planes), improve
thermal coupling to the module (e.g. by conducting heat through a
mounting board or substrate), and/or provide solder-mount options.
Additionally, the plated conductive layer may slow moisture
absorption by the encapsulant (e.g., 102, 103), protect magnetic
cores, and help control leakage inductance in internal
transformers.
The shield 150 may optionally make electrical connection to edges
of the PCB along the perimeter of the module, i.e. along the cut
lines, using the bar code techniques described in the Panel Mold
Disclosures, e.g. using the techniques described in the
Multi-Surface Application. However, the shield may instead, or
additionally, be electrically connected to conductive traces in the
PCB 101 via the apertures 160-1, 160-2, 160-3, 160-4, using the
process described below. Of course, the electrical shield 150 need
not make electrical connection to internal circuitry, or to the PCB
101 at all, remaining electrically isolated. As also shown in FIG.
1, the module 100 may comprise apertures, e.g. apertures 160-1,
160-2, 160-3, 160-4, which may preferably extend all the way
through the module, which may for example provide holes for
mounting the module to a larger assembly. The apertures 160-1,
160-2, 160-3, and 160-4 may additionally be used for electrical
connections, e.g. a ground or common terminal, and facilitate heat
removal by mounting the module to a cold plate, heat sink, or other
heat removal device.
A. Panel Preparation
A process for making the electronic modules 100, illustrated in
FIGS. 3 through 6 builds upon the panel molding processes described
in the Panel Mold Disclosures focusing on making terminals 130,
140, 170 and apertures 160. In the example of FIGS. 3-6, the
encapsulated panel 190 comprises four un-singulated electronic
modules 100A, 100B, 100C, 100D, which when finished will include a
conductive shield 150 connected to the edges of the PCB 101. Note
that the electrical terminals, e.g. 130-1, 130-2, 140-1, 140-2, and
170 (FIG. 1) may be formed in module 100 with or without the
optional electrical connections, e.g. to the shield 150, to the
edges of the PCB 101 along the cut lines.
The following process description starts from just after the PCB
panel is encapsulated as described in the Multi-Surface
Application. The encapsulated panel 190 which is partially shown in
the example of FIGS. 3 through 6 comprises four un-singulated
electronic modules. (See also, encapsulated panel 890 shown in
FIGS. 43-44 of the PM CIP and panel 102-1 in FIGS. 4-9 of the
Multi-Surface Application.) Note that the panels in the Panel Mold
Disclosures (which are assumed to be the same size as in the
present example) are shown comprising a larger number of
un-singulated electronic modules 100, reflecting the dependency on
module size, e.g. the relatively larger modules 100 in FIGS. 3-6,
results in fewer modules per panel.
As shown in FIG. 3, the panel 190 is shown with several cut lines
191 through 198 representing the edges of a plurality of
un-singulated modules, 100A, 100B, 100C, 100D: cut lines 191, 192,
193, 194 representing boundaries between adjacent modules and cut
lines 195, 196, 197, and 198 representing the boundaries between
modules and scrap material. Electronic components and conductive
features associated with each module are included within the
respective cut lines defining the boundaries of the module. The
modules 100A-100D remain integral parts of the encapsulated panel
190 until separated from the panel by singulation cuts. Also shown
in FIG. 3 are exposed, e.g. non-encapsulated, areas e.g. features
180-1, 180-2, 180-3, 180-4, 180-5, of the surface of PCB 101 that
may be provided to locate reference holes or fiducials for
alignment or identification of the panel during manufacture. (See
col. 30, ln. 24-col. 30, ln. 46 in the PM CIP).
Holes, including blind holes and through holes, may be formed in
the encapsulated panel 190 to establish the locations of the
terminals and apertures. (As used herein, a blind hole refers to a
hole that extends partially into, but not completely through, the
panel; and a through hole refers to a hole that extends completely
through the panel.) For example, FIG. 3 shows blind holes 136-1,
136-2, 146-1, 146-2 and 176 (e.g. 176-1, 176-2, 176-3, 176-4,
176-5) and through holes 160-1, 160-2, 160-3 and 160-4 formed in
un-singulated module 100A, corresponding to the locations of
terminals 130-1, 130-2, 140-1, 140-2 and 170 (i.e. 170-1, 170-2,
170-3, 170-4, 170-5) and apertures 160-1, 160-2, 160-3 and 160-4
shown in FIG. 1. Corresponding holes (not labeled) are shown formed
at corresponding locations on the other modules 100B, 100C, 100D on
the panel 190. The mounting holes, e.g. 160-1, 160-2, 160-3, 160-4,
preferably may be formed as through holes, which extend completely
through the module, allow mounting hardware to pass through the
module; while the holes, e.g. 136-1, 136-2, 146-1, 146-2 and 176,
for the terminals, e.g. 130-1, 130-2, 140-1, 140-2 and 170 (i.e.
170-1, 170-2, 170-3, 170-4, 170-5), may be blind holes providing
electrical isolation between each terminal and the shielding or
mounting surfaces on the opposite side of the module, e.g. chassis,
cold plate, heat sink or other heat removal structure without the
need for added insulation.
Holes 136-1, 136-2, 146-1, 146-2 and 176 (for the terminals) each
may therefore be preferably formed to extend partially through the
thickness of the module to expose conductive features buried within
the module for making electrical connections from one side of the
module, but not extend so far as would require insulation on the
opposite side; and more preferably, extend only as deep as required
to expose the conductive features necessary for each terminal.
Referring to FIG. 7A, which shows a cross-section though module
100A at the center of blind hole 136-2, shows the depth of the
blind hole, D.sub.1, (FIG. 7A) extending all the way through
encapsulant layer 103, all the way through PCB 101, and into but
not through, e.g. part of the way through, encapsulation layer 102,
i.e. the depth, D.sub.1, is less than the thickness, T of the
module. As shown blind hole 136-2 is preferably formed to expose
conductive features buried in the module. As shown in FIG. 7A, the
hole may be formed to pass through the conductive features, e.g.
conductive features 200-1, 200-2, 200-3, 200-4, representing traces
in layers of the multilayer PCB 101, exposing one or more layers of
conductive traces on the inner surfaces (e.g. surfaces 210-1,
210-2) of the hole 136-2. As shown in FIG. 7A, the hole passes
through conductive traces located in more than one of the
conductive PCB layers producing conductive rings in the wall of the
hole 136-2, akin to the bar code terminations described in the PM
CIP, Bar Code Patent, and Multi-Surface Application.
A more detailed description of buried interconnects and bar codes
may be found in the PM CIP at col. 17, ln. 36-col. 19, ln. 14, in
the Bar Code Patent at col. 15, ln. 40-col. 17, ln. 2; and at
paragraphs 036 and 037 of the Multi-Surface Application. The bar
codes described in the PM CIP, Bar Code Patent, and Multi-Surface
Application may be formed primarily along module boundaries and
exposed during singulation in the PM CIP and Bar Code Patent or
before singulation in the Multi-Surface Application. The bar codes
in the Multi-Surface Application are exposed in a similar fashion,
e.g. by forming holes to expose the buried conductive features;
however, the process in the present disclosure forms the holes and
exposes the conductive features in areas of the module that may not
include the cut lines, i.e. are located completely within the
boundaries of each individual module, rather than along the
boundary, and preferably result in one or more conductive rings in
the side walls of the holes (which are undisturbed by singulation).
The conductive features exposed by forming the holes may preferably
result in conductive rings embedded in the inner surface of the
holes, however, they need not. For example, the conductive rings
are formed when the hole passes through a horizontal conductive
layer that completely surrounds the hole. For conductive features
that are not horizontal relative to the vertical axis of the hole
or that may not completely surround the hole, the shape of the
conductive feature exposed in the inner surface of the hole, i.e.
the hole wall, may differ. For example, a hole may pass through
only a portion of a conductive feature such as a puck on the
surface of, or a conductive layer in, the PCB 101, so the
conductive feature may not be present in the entire circumference
of the hole, thus not appearing as a ring. For simplicity the
following description will refer to the conductive features exposed
in the holes as "conductive rings" consistent with the embodiment
having holes that penetrate the PCB, but the term should be
understood to refer generally to any conductive feature exposed by
forming the hole. For example, the conductive rings can have a
circular shape, an elliptical shape, a star shape, or any other
shape of the hole. The conductive rings may not completely surround
the hole and may not be horizontal relative to the vertical axis of
the hole. In some examples, the conductive features exposed in the
holes are considered to be edges of the conductive layers. In the
case of a conductive puck on a surface of the PCB, the exposed
feature may appear as a single conductive sleeve in the hole.
The cross section through the centers of blind holes 176 in FIG.
7C, shows the depth, D.sub.2, of the holes 176 relative to the PCB
101 and encapsulation layers 102, 103. As shown blind holes 176
extend completely through encapsulant layer 103, partially into but
not completely through PCB 101, and not at all into encapsulation
layer 102. Controlling the depth, e.g. depth D.sub.2, during
formation of the blind holes, e.g. holes 176, allows selective
exposure of buried conductive features, e.g. conductive PCB traces
exposed as one or more conductive rings on the inner surface of the
hole and greater utilization of other layers of the PCB. For
example, conductive traces 200-6, 200-7, 200-8 and 200-9 are shown
exposed in blind hole 176-3 while conductive traces 200-10, 200-11
are not exposed in FIG. 7C.
Alternatively, blind holes may be formed to avoid penetrating the
internal substrate in the panel. Referring to FIG. 7B, the depth,
D3, of the holes, e.g. hole 136-2B, is shown avoiding penetration
of the PCB 101. As shown, hole 136-2B extends to the surface of the
PCB 101, which in the example shown, exposes a conductive feature
200-5 at the bottom of the hole. In this variation, the conductive
feature may appear as an essentially flat conductive surface at the
bottom of the hole having a perimeter that essentially matches that
of the hole. For convenience, the term "conductive plate" will be
used herein to refer to the conductive features 210-5 exposed at
the bottom of blind holes that do not penetrate the PCB 101
irrespective of the shape of the hole. A laser may be particularly
adept at forming holes of the type shown in FIG. 7B, where the
wavelength of the laser may be chosen to selectively remove the
encapsulant, e.g. encapsulant 103, at an efficient rate, but does
not significantly remove conductive features, e.g. copper traces on
the surface of the PCB 101, or conductive features mounted to the
surface of the PCB 101, in which case the conductive feature to be
exposed may be used to control the depth of the hole. For example,
the laser wavelength may be chosen to provide a removal rate of
encapsulant that is one or more orders of magnitude greater than
the removal rate of copper. Laser drilling may be preferable over
mechanical drilling for the precision of the hole depth which may
be controlled by the conductive feature. Additionally non-circular
holes may be more easily formed with the laser compared to a
mechanical drill or router. For example, oval slots and other hole
shapes are easily formed with the laser, e.g. non-circular holes
may provide venting during soldering, e.g. allowing use of simpler
terminals, i.e. without ridges along the shank, to save cost, and
may resist rotation of the terminals, i.e. to provide improved
mechanical integrity; or be shaped to facilitate plating processes,
e.g. to improve metal deposition in the holes.
Optionally, electrically conductive features may be mounted to the
PCB 101, e.g. on one or both surfaces of the PCB 101, remain buried
within the encapsulated panel, and exposed by forming the holes
176; with the advantage of increasing the exposed area of the
conductive rings for holes that penetrate the conductive feature or
the performance of the conductive plate or to provide a buffer for
laser drilled holes in the FIG. 7B variation.
By limiting the depth, D, of holes to be less than the thickness,
T, of the module (e.g., D.sub.1<T, D.sub.2<T, D.sub.3<T)
no part of the terminals (e.g. terminals 130) are exposed at the
outer surface of encapsulation layer 102. This may provide enhanced
insulation and safety and make the outer surfaces of layer 102
adjacent to the holes available for plating with shields or other
conductive patterns. Partial depth holes may also result in better
mechanical support for terminals.
Optionally, electrical connections to the PCB 101 along the
perimeter of the individual modules, e.g. module 100 (FIG. 1) may
be established using the process descried in the Multi-Surface
Application. For example, the shield 150 shown in FIG. 1 may be
electrically connected to the PCB along one or more of the four
edges of the module using the Multi-Surface process. Accordingly in
FIG. 4, panel 190 (which comprises four un-singulated electronic
modules) is shown having optional slots, e.g. slots 221 through
228, formed in the panel, e.g. cut all the way through the panel as
described in the Multi-Surface Application, along the cut lines
191-198 to establish electrical connections at the edges of the PCB
101. Cutting of slots of this kind may be done using, e.g. a water
jet as described in the Multi-Surface Application at paragraph 38.
The connections formed along the module perimeter, via the slots,
may be used in addition to electrical connections formed via the
holes 160, e.g. to improve electrical performance. Of course,
connections along the perimeter of the module may be omitted in
which case forming the slots before plating also may be
omitted.
FIG. 5 shows the panel 190 after a conductive layer has been
formed, e.g. by plating, on selected surfaces of the module,
including the surfaces within slots 221 through 228, and patterned
as described in the Multi-Surface Application. The conductive layer
150 in FIG. 5, corresponding to conductive shield 150 in FIG. 1,
may as shown provide a continuous conductive shield covering the
outer surfaces of the encapsulant layers 102, 103 and the sides of
the modules exposed within the slots 221, 223, 226. Alternatively,
the shield may be patterned to cover select portions of the
surfaces as desired, e.g. the shield 150 may preferably cover at
least 25 percent, or 50 percent or more of the module surfaces.
Preferably, the process of forming the conductive layer deposits
conductive material inside of the exposed holes and optional slots,
e.g. blind holes 136-1, 135-2, 146-1, 146-2 and 176, through-holes
160-1, 160-2, 160-3 and 160-4; and on the exposed surfaces of the
panel, e.g. in regions 231, 232, 233, and 234 on the module
surface, adjacent to the holes providing a conductive layer around
each hole, i.e. a conductive pad. Plating within the holes may form
a conductive connection to the conductive bar code pattern(s) or
conductive plate(s) on the inner surfaces of the holes and slots. A
variety of processes for providing conductive material on panel
surfaces and in the slots and holes, e.g. using plating processes
which may include masking, deposition of a seed layer, and
electroless or electrolytic plating of copper, are described in
paragraphs 40-48 in the Multi-Surface Application. As shown, the
conductive layer is patterned to provide conductive material on the
surface surrounding each hole that preferably extends into the hole
making electrical contact with the exposed conductive features,
e.g. conductive rings or conductive plate in the hole. The
through-holes, 160-1, 160-2, 160-3 and 160-4, in the example of
FIG. 5 may be formed, as shown, in the area in which the conductive
shield is to be formed, and the conductive layers formed on the
exposed interior surfaces of the through-holes can be connected to
the conductive shield, which may additionally be connected to
either bar codes along the module perimeter edge as shown,
conductive rings within each through-hole, or both. Alternatively,
one or more through holes may be electrically isolated from the
shield by appropriate patterning of the shield in the manner shown
for the blind-holes 136 in FIG. 5.
FIG. 6 shows a portion of the panel 190 after the singulation cuts
have been made, dividing the panel into individual modules.
Singulation methods, which may include cutting along cut lines
(e.g. cut lines 191-198, FIG. 3) within the slots (e.g. slots
221-228, FIGS. 4 and 5) using a thin saw, e.g. 0.012'' blade, are
described at col. 17, lns. 7-34, in the PM CIP and paragraph 49 in
the Multi-Surface Application. Because the plating step provided
plating within the slots, a continuous shield 150 may be formed on
multiple surfaces of the modules, as shown in FIGS. 1 and 6.
Exposing bar codes along the perimeter edge of the module for
making electrical connection to the conductive shield, which is not
necessary for the present embodiment, may be supplanted or
augmented with connections formed within the through-holes. For
example, the slots along the perimeter edges of the modules (e.g.
slots 221-228, FIGS. 4 and 5) may be omitted completely, in which
case the conductive shield may be absent from the vertical edges of
the singulated modules and may be patterned to include a setback
from the vertical edges if desired.
B. Terminal Assembly
The terminals may be assembled to the module before or after
singulation, each approach having its own advantages and
disadvantages. For example, terminal assembly before singulation
may be advantageous for standardized panel handling equipment but
would present cleaning challenges following singulation.
Conversely, terminal assembly following singulation avoids
subjecting the terminals to singulation residue in the terminals
which may be preferable even with potential module-specific
assembly challenges. Referring to FIG. 2, an exploded view of a
module 100 is shown with terminals 130-1, 130-2, 140-1, 140-2 and
170 prior to insertion into and assembly with their respective
plated holes 236-1, 236-2, 246-1, 246-2 and 276. Terminals may be
secured within their respective holes in a variety of ways,
including, e.g., soldering or press-fitting, and the configuration
of the portion of a terminal that is inserted into a hole may be
adapted as desired according to the function, configuration and
size of the terminal and the method of insertion.
Referring to FIG. 8A which shows a detailed cross-sectional view of
terminal 130-2 assembled with a respective PCB-penetrating plated
hole 236-2 (FIGS. 7A, 7C). As shown, conductive plating 237 on the
inside surface of the hole 236-2 is electrically connected to the
conductive rings, i.e. the exposed conductive layers of PCB 101
(e.g. conductive layers 200-1 through 200-4). As shown, the region
between the interior plated surface of the plated hole 236-2 and
the exterior surface of the terminal 130-2 within the hole may be
filled with solder 250 to form a robust electrical and mechanical
connection. To allow gases to escape from the hole during the
soldering process, the terminal 130-2 may include contours to
provide clearance between the terminal 130-2 and the interior
surface of the hole (e.g. dimension W, FIG. 8A). For example, FIG.
2 shows terminals 130-1, 130-2, 140-1, 140-2, having an
approximately octagonal shape, which provides gaps between the flat
surfaces 270 of the terminal and the circular walls of the hole.
Other contours, shapes, or indentations may be provided to allow
gases to escape from the holes during soldering.
Referring to FIG. 8B, a cross-sectional view of terminal 130-2
assembled with a respective non-PCB penetrating plated hole 236-2B
is shown with conductive plating 237 on the inside surface of the
hole 236-2B. The conductive plating 237 in the embodiment shown in
FIG. 8B is electrically connected to the exposed metal layer on the
surface of the PCB 101, i.e. the exposed top conductive layer of
PCB 101 (e.g. conductive layer 200-5). Similar to the embodiment of
FIG. 8A, the region between the surface of conductive layer 237 in
the plated hole 236-2B and the exterior surface of the terminal
130-2 within the hole may be filled with solder 250 to form a
robust electrical and mechanical connection. Gases may be allowed
to escape from the hole during soldering in the clearance between
the terminal 130-2 and the interior surface of the hole (e.g.
dimension W, FIG. 8B) which may be provided using differences in
shape between the hole and the terminal 130-2.
At first glance, comparison of FIGS. 8A and 8B, may suggest a
current carrying advantage in FIG. 8A which inherently allows the
current through the terminal to flow through a plurality of the PCB
layers vs a single layer in FIG. 8B. However, the surface area of
the exposed conductive feature 210-5 making contact with the
conductive layer(s) 237 in the hole in FIG. 8B may be much greater
than the embodiment on FIG. 8A (depending on the number and
thickness of exposed layers and the surface area of the hole) and
limitations on the number and placement of conductive vias that may
be distributed, e.g. within and around, each hole may be negligible
in the embodiment of FIG. 8B compared with FIG. 8A because wear on
a mechanical drill bit is not a concern with the laser formed
holes. Thus, in the embodiment of FIG. 8B, with a laser drill, a
plurality of conductive vias may be distributed in and around the
area of the hole 136-2B to connect to a plurality of conductive
layers for a more robust electrical and thermal connection.
The cross-sectional views of FIGS. 9A and 9B show terminals 130-1,
130-2 and 170-3 soldered into their respective PCB-penetrating
plated holes 236-1, 236-2, 176-3 (FIG. 9A) and non-PCB-penetrating
holes 236-1B, 236-2B, 176-3B (FIG. 9B) and four terminals 170-1,
170-2, 170-4, 170-5 which may be press-fit within their respective
PCB-penetrating plated holes 176-1, 176-2, 176-4, 176-5 (FIG. 9A)
and non-PCB-penetrating plated holes 176-1B, 176-2B, 176-4B, 176-5B
(FIG. 9B) as described below.
In some embodiments, one or more conductive components, e.g.
conductive pucks 300 (FIGS. 10, 11), may be mounted on a surface,
or surfaces, of the PCB 101 prior to encapsulation in locations
that enable the conductive component to be exposed by the formation
of a terminal hole. FIG. 10, which shows an isometric view of a
module with the top layer of encapsulant removed, provides another
example of a conductive component 300 arranged on the surface of
PCB 101. The conductive component 300 may, e.g. be a copper plate
or bar as shown or may have any suitable shape for the application.
The dashed line 400 in FIG. 10 shows a location where a terminal
hole may subsequently be formed. As shown, a hole 410 may be
optionally provided in the conductive component near the intended
terminal hole 400, e.g., to minimize wear on equipment, e.g. a
drill, used to form the terminal hole, or decrease the process time
for forming the hole, e.g. because of less metal requiring removal.
Preferably, the hole 410 would be located, e.g. completely within,
the intended terminal hole 400, to allow the formation of the
latter to completely define the portion of the conductive component
that is subsequently exposed in the terminal hole, providing
improved accuracy and ensuring the terminal pin adequately engages
the conductive component. In embodiments in which the terminal hole
does not penetrate the PCB 101, the hole 410 may be omitted.
FIGS. 11A, 11B, 11C and 11D show several examples of alternate
configurations using conductive components on one or more of the
PCB surfaces. In FIG. 11A the conductive component 300 is placed on
a top surface of the PCB 101 in contact with conductive trace 205,
so that the plated terminal hole 236 passes through it. The plating
237 in the hole connects to exposed conductive rings 200-1 through
200-4 in the hole and to the conductive component 300. FIG. 11B
shows a configuration in which the terminal hole 236 passes through
conductive components 300a, 205a, 205b, 300b that are located on
both top and bottom surfaces of the PCB 101. FIG. 11C shows a
configuration in which the bottom of the terminal hole 236 contacts
the conductive component on the surface of PCB 101. FIG. 11D shows
a configuration in which the bottom of the non-PCB-penetrating
terminal hole 236 contacts the conductive component 300 on the
surface of PCB 101. A conductive component may be located over, and
may be soldered to, a conductive trace on the PCB at the location
of the terminal hole (e.g. conductive traces 205, 205a, 205b); it
may be placed over bare portions of the surface of the PCB 101 at
the location of the terminal hole and be connected at another
location to circuitry on the PCB 101 (i.e. a bus bar); or it may be
placed on a bare portion of the PCB only (i.e. for mechanical
support). The examples of FIG. 11A through 11D are illustrative; it
is understood that there are many possible configurations of
conductive components and terminal holes. By providing additional
cross-sectional area in the conduction path, the conductive
component may reduce the equivalent series resistance of a
terminal. It may also provide increased mechanical strength and
rigidity.
An example of press-fit pin terminals will be described with
reference to FIGS. 12 and 13, which respectively show a press-fit
pin 170; and a magnified view of a portion of FIG. 9A that includes
pins 170-1, 170-2, 170-3, 170-4, 170-5. As shown in FIG. 13, an
optional conductive component, e.g. "puck" 260, is soldered or
otherwise electrically connected to a respective conductive trace
or pad (e.g. pad 220) on PCB 101 for each of pins 170-1, 170-2,
170-4, 170-5 in the pin's respective location. Each puck is
preferably made of a malleable electrically conductive material,
e.g. copper, may form a substantial part of the electrical
connection between the pin and the respective PCB trace, and
provide mechanical support for the press-fit pin. The conductive
features, e.g. puck 260, may be buried by the encapsulation
process, after which, each puck may be exposed by formation of a
respective hole, e.g. PCB-penetrating holes 176-1, 176-2, 176-3,
176-4, 176-5, e.g. drilled. Each hole may pass through encapsulant
layer 103 and, in the example shown, through the respective puck
260 and optionally through all, or preferably only a portion of,
PCB 101. As indicated in FIG. 13, the hole preferably may be formed
to have a diameter X of an upper portion that is larger than a
diameter Y of a lower portion (e.g. by use of two drill bits or a
single stepped drill bit, etc.). The press-fit pin 170, shown prior
in FIG. 12, may have a lower portion 178 that is larger in diameter
than an upper portion 179 (i.e., in FIG. 12, diameter B is greater
than diameter T). The diameter B of the pin lower portion 178 may
be greater than the diameter, Y, of the lower portion of hole
176-2, but preferably less than the diameter X of the upper portion
of hole 176-2 to facilitate compression of the lower portion of the
pin 178 by the smaller internal diameter of the puck 260 when pin
170-2 is pressed into hole 176-2. This frictional compressive fit
may secure the pin mechanically and may also ensure a low
resistance, high quality, electrical connection between the pin and
the conductive puck. In some applications, adhesive may be placed
between the head of pin 170 and the surface of encapsulant layer
103 (e.g. at location 285, FIG. 13). Alternatively, the press-fit
pins 170 may engage with the sidewall of the holes without the use
of conductive pucks mounted to the PCB, e.g. directly with either
the PCB or with the metalized holes.
It should be appreciated that plating inside of one or more of
through-holes 160-1, 160-2, 160-3, 160-4 (FIGS. 1, 3, 5) may
connect to circuitry on the PCB 101, e.g. connecting the shield 150
to internal circuitry within the module, e.g., to a circuit ground.
Similarly, the plating inside the one or more blind-holes, e.g.
holes 136-1, 136-2, 146-1, 146-2, 176-1, 176-2, 176-3, 176-4,
176-5, may selectively connect to portions of the internal
circuitry providing electrical terminals, such as power input,
power output, and control signals in the case of a power
converter.
A wide variety of terminal and mounting configurations are
possible. FIG. 14, for example, shows a module 100 having terminals
530-1, 530-2, 540-1, 540-2 comprising columnar studs that extend
beyond a surface of the module and that may be used to connect the
module, as illustrated in FIGS. 15 and 16, to an external printed
circuit board 600 or connectors. In FIGS. 15 and 16, the module 100
is secured to the external PCB 600 by means of screws 960-1 through
960-4, which pass through through-holes 160-1 through 160-4, and
threaded nuts or inserts 980-1 through 980-4. Columnar studs on
terminals 530-1, 530-2, 540-1, 540-2 pass through holes in external
PCB 600 and may be soldered to etches (not shown) on the external
PCB or alternatively may engage with connectors (not shown). FIG.
17 shows an exploded view of another configuration in which ring
lugs 730-1, 730-2, 740-1, 740-2 are secured to respective
internally threaded terminals 130-1, 130-2, 140-1, 140-2 by means
of screws 970-1 through 970-4. In FIG. 17, mounting screws 960-1
through 960-4 may be inserted into through-holes 160-1 through
160-4 to secure the module to, e.g. an external chassis or heat
sink assembly (not shown). It should be appreciated that a wide
variety of terminal shapes and sizes may be used. For example,
terminals may be inserted into the holes that may be sized, cut, or
ground to be coplanar with the surface of the finished module, or
extend slightly above or below the module surface to provide
connection bumps, or indentations.
II. Surface Mount Trench Terminals
An alternative "trench" type terminal may be used without the
terminal inserts, e.g. inserts 130-1, 140-1, (FIGS. 1-2, 8-9),
inserts 530-1 540-1 (FIG. 14), pins 170-1, 170-3 (FIGS. 1-2, 12-13)
described above. Referring to FIGS. 18A and 18B, which partially
show encapsulated panels 190-2, comprising a large multiplicity of
un-singulated electronic modules, e.g. 100-2A, 100-2C, each having
a plurality of electrical trench terminals, e.g. terminals 137A,
137B, 137C, 137D (FIG. 18A). The example of FIGS. 18A and 18B
assumes panels 190-2 of the same size, and un-singulated modules,
e.g. 100-2A, 100-2B, 100-2C, 100-2D, 100-2E, 100-2F, of a size much
smaller than, those (panels 190, un-singulated modules 100) in the
previous examples of FIGS. 1-6 and 14-17. The un-singulated
modules, 100-2, may be delineated by cut lines 191, which in
contrast to the example of FIGS. 1-6, do not pass through any
metalized slots or holes as shown in FIGS. 18A, 18B, i.e. the
perimeter contacts described in the Multi-Surface Application are
not employed in this example. The trench terminals 137A, 137B,
137C, 137D as shown in FIG. 18A are unfilled plated holes (see
Insert 18A for a magnified view of an unfilled plated hole) in
contrast to the trench terminals 138A, 138B, 138C, 138D shown in
FIG. 18B as filled (see Insert 18B for a magnified view of a filled
plated hole). The plated holes may be filled partially or
completely with a curable compound, e.g. epoxy, preferably
conductive, to leave a controlled volume of the trench unfilled,
e.g. the controlled volume may range from 0 to 100 percent
unfilled, for subsequent solder deposition or additional plating
onto the cured compound in the trench or hole. Alternatively, the
trench terminals may be filled partially or completely during the
plating process, e.g., by plating, leaving a dimple or
approximately flat pad, in or on which solder paste may optionally
be deposited.
The metal formed on a surface of the modules 100-2 may be patterned
as necessary for the application, e.g. in FIGS. 18A, 18B the metal
on the top surface is shown patterned into strips, e.g. metal
strips 232-1A, 232-1B, and 232-1C, for a power converter
application. Each strip 232-1A, 232-1B, and 232-1C, may include a
plurality of trenches, 137B, 137C, and 137D, respectively providing
a plurality of connections to each metal strip, for example to
provide high current connections, as shown in FIG. 18A. One or more
additional trench terminals 137A may be isolated from the metal
strips 232-1A, 232-1B, 232-1C to provide lower current signal
connections, e.g. timing and control signals, to the module, e.g.
at an end of each module as shown in the example of FIGS. 18A and
18B. Typically, one surface of the module may be dedicated for
electrical connections to the system in which it is installed, e.g.
surface mounted, and the opposite surface may be use for shielding
and or heat removal, e.g. attached to a heatsink or cold plate, in
which case the metal may cover the entire opposite surface with or
without a setback from the edges of the module, e.g. cut lines 191.
The metal on the opposite surface, e.g. the shield, may also
include trench terminals of the type shown in FIGS. 18A and 18B.
The trenches in the surface of the panel may be partially or
completely filled, e.g. with one or more fillers to form the
terminals, e.g. the trenches may be partially filled with a curable
compound such as an epoxy and then filled with solder paste for
subsequent attachment to a system board or other device. For
example, the curable compound may be cured before filling or
partially filling the trenches with the solder paste.
III. Fabrication Process Flow
The processes for fabricating the above modules using insert
terminals or trench terminals are summarized in the flow charts 610
and 620 of FIGS. 19A and 19B. The process 610 in FIG. 19A
illustrates the preferred singulate before terminal assembly method
described above for building modules with terminal inserts. The PCB
panels may be assembled as shown in step 601, e.g. attaching the
various components to the PCB; the assembled panels being
encapsulated in step 602, and the encapsulated panels being lapped
in step 603, e.g. for thickness and planarity control. The terminal
holes, e.g. blind holes 176, 136, and 146 (FIG. 3), through holes
160 (FIG. 3), and optional slots 221, 225, 226 (FIG. 4) may be
formed, preferably using a laser to remove the encapsulant to a
controlled depth, preferably to the first metal layer on the PCB
for the blind holes, and then panels may be cleaned as shown in
step 604. The panels may be metalized as shown in step 605, which
may include forming metal inside the holes and optional slots, and
may include additive or subtractive patterning to form the
requisite pattern, e.g. metal shield, clearance between terminal
holes and shield, and conductive features on the surface around the
terminal holes, e.g. in regions 231, 232, 233, 234 (FIGS. 5-6) on
the surfaces of the panels as described above. The panel may be cut
to singulate the individual modules which may then be cleaned as
shown in step 606A; after which solder may be dispensed to the
blind terminal holes as shown in step 607A. The terminals may be
inserted into their respective holes as shown in step 608A and the
solder reflowed as shown in step 609A to complete the process.
The singulate and clean step 606A of process 610 may be moved to
the end after the reflow step 609A should the terminal assembly
before singulate process be preferred.
It will be appreciated that any size or shape solder terminals may
be provided according to the needs of the application. Finally, the
panels may be cut along the cut lines, e.g. lines 191-198 in FIG.
3, to singulate the individual modules, e.g. modules 100A, 100B
(FIG. 3).
The trenches for the trench terminals may be formed using the same
techniques described above for holes 136-2B in FIG. 7B. For
example, the process for making the trench terminals may start from
just after the PCB panel is encapsulated as described in the
Multi-Surface Application and may preferably use
non-PCB-penetrating holes similar to those described above in
connection with FIG. 7B, however, the size of the holes for forming
the trench terminals is preferably much smaller than those
described above for the terminal inserts, and may preferably have
non-circular geometries, e.g. length to width aspect ratios that
allows for effecting metal plating in the holes, all making them
particularly amenable to formation by laser drilling. As shown in
FIG. 18A, the trench holes 137A, 137B, 137C, and 137D, may be oval
slots for example. Slots may be preferable to round holes for small
hole dimensions to allow the inner walls of the slot to be plated
during subsequent metal layer formation.
The process 620 for fabricating the trench terminals is summarized
in FIG. 19B, which shows the PCB panels being assembled in step
601, the assembled panels being encapsulated in step 602, the
encapsulated panels being lapped in step 603, e.g. for thickness
and planarity control, and then the trenches, e.g. slots, are
formed, preferably using a laser to remove the encapsulant to a
controlled depth, preferably to the first metal layer on the PCB
and the panels cleaned in step 604, and then metalized in step 605,
which includes forming metal inside the trenches or slots, and may
include additive or subtractive patterning to form the requisite
conductive features, e.g. metal strips, signal terminals, and
shields on the surfaces of the panels as described above. The slots
may optionally be substantially filled with metal by the plating
process, or alternatively filled afterward with a curable compound,
which may preferably be conductive as shown in step 606B. Solder
may be dispensed to the filled or unfilled slots as shown for step
607B and then may be optionally planarized, e.g. by applying a
compressive force, to a controlled height, e.g. a uniform height
for the dispensed solder as shown in step 608B. Finally, the panels
may be cut along the cut lines, e.g. lines 191 in FIGS. 18A and
18B, to singulate the individual modules, e.g. modules 100-2A,
100-2B (FIGS. 18A and 18B).
Several embodiments of the invention have been described.
Nevertheless, it will be understood that various modifications may
be made without departing from the spirit and scope of the
invention. For example, it will be appreciated that any size or
shape terminal or trench may be provided according to the needs of
the application. Although a continuous shield 150 has been shown
above as an example of plating on the surface of a module, the
plating may be configured in a virtually limitless number of ways,
including forming electrical contacts on the outside of the module
that enable connecting internal module circuitry to external
components or other modules. Examples of "bar code" etches shown
herein were limited, for clarity of illustration, to relatively few
layers on the internal PCB. The number of layers in a particular
embodiment is a function of the application and may be relatively
small (e.g. 2 layers, 5 layers) or relatively large (e.g., 11
layers, 30 layers).
Accordingly, other embodiments are within the scope of the
following claims.
* * * * *
References